The present invention is related to networks and switches for the transmission or transfer of data packets or data cells and in particular a processing performed at the incoming and outgoing sides of a switch involving a translation of the labels, which data packets carry for identifying that they belong to a particular logical connection established through the network and the switch.
This application claims priority from Swedish Patent Application No. 9300793-8, filed Mar. 10, 1993, which is incorporated here by reference.
In a data packet network it is required, in the transfer of data packets from sending units to receiving units through various nodes in the network, that each data packet can be uniquely assigned a connection, which has been established earlier in the setup of the logical connection through the network. It is achieved by providing the data packets with labels, i.e. a special field comprising identification information. In the transfer in the network through many nodes, where the data packet is switched from an incoming connection line to an outgoing connection line, it may occur that data packets have been provided with the same label what will cause difficulties or even errors in the transmission.
Data packets belonging to different types of established connections may in addition have label fields of different formats, e.g. such that data packets belonging to some connections have a shorter label field while data packets belonging to other connections also have such a short label field but also in addition thereto a longer label field. In the second case the first short label field may then indicate a group of connections, of which the connection is a part. Such different parts may be present when for instance some established connections are assigned more permanent paths in the network than other connections. These different formats result in further problems in the processing of the labels of the individual data packets.
The data packets considered here are in the common way transmitted through the network from one end station to another end station. The end stations are then provided with a single connection interface, both for sending and for receiving, coupled through a connection line to an associated connection node in the network. Special format restrictions may then be valid for the labels depending if a data packet is transmitted directly from such an end station or is received by an end station or if a data packet is in the process of being forwarded between two switching nodes in the system.
The handling of in particular addresses in data packets is disclosed e.g. U.S. Pat. Nos. 4,894,822; No. 4,218,756; No. 3,979,733; and No. 4,494,230; and in European Patent Applications EP-A2 0 282 197 and EP-A2 0 206 403, and in Soviet Patent Application SU-A 478 445.
In the European patent application EP-A2 0 406 842 a packet switch network is disclosed comprising label processing at incoming and outgoing links of a switch. Therein the numbers in data packets identifying the logical connection--VP or VC number--are substituted by new numbers found in lists stored in memories at the incoming and outgoing sides of the switch. When many logical connections are to be simultaneously active, the lists will be correspondingly long and memory space therefor must be provided in the construction of the switch.
Label processing is also disclosed in European Patent Application EP-A2 0 481 447, and in U.S. Pat. Nos. 4,947,388; No. 5,099,475; No. 4,995,032; and No. 5,166,926.